Polymerization processes for producing polymers, such as polyolefins, typically require removal of unreacted monomers and solvents from final product. The monomers and solvents are often subsequently recycled back into the polymerization process. Usually, removal of the monomers and solvents is achieved through devolatilization of the polymerizate stream exiting the reactor, such as a molten polymer stream. Devolatilization of polymers is typically achieved by both raising the temperature and lowering the partial pressure of the volatile components. Lowering partial pressure can be accomplished by using a vacuum or by introducing a gaseous diluent at a fixed total pressure. Examples of gaseous diluents, also known as stripping agents, include steam, carbon dioxide, water, and methanol. However, such gaseous diluents can poison the catalyst system; thus, further processing steps are required to remove those gaseous diluents from a recycle stream containing monomer and solvent before the recycle stream can be introduced back into the polymerization step. For example, if a non-condensable gaseous diluent, such as nitrogen, is used, a further process step of venting is required to avoid build-up of nitrogen in the system. However, venting of nitrogen can also result in loss of other desired volatile species, such as monomers, which can be vented along with nitrogen. Additionally, when using gaseous diluents, such as water and methanol, a further separation and removal process is needed to remove water and methanol from a condensed overhead stream resulting in additional cost and time during the polymerization process.
Thus, there is a need in the art for new and improved polymerization processes where devolatilization of the polymer can be achieved with stripping agents that do not poison the catalyst systems, and subsequently can be recycled back into the polymerization process without further processing steps. The present disclosure provides polymerization processes where devolatilization of the polymer is achieved by a non-polar and condensable stripping agent that does not require removal from the process and can be recycled back to the polymerization step.